The present invention relates to a method for making an electrical circuit board and more particularly, to a method for making a multi-layer electrical circuit board having interconnections between portions or layers of the circuit board.
Multi-layer circuit boards contain and/or include electrical components which selectively and operatively populate opposed first and second surfaces (i.e., top and bottom surfaces) of each board (or other respective interior portions of each of the boards), thereby desirably allowing each of the electrical circuit boards to contain and/or include a relatively large amount of electrical components which efficiently and densely populate the respective boards.
It is desirable to allow for communication by and between and/or interconnection of the component containing surfaces and/or portions of an electrical circuit board, thereby allowing the contained electrical components on each side of the board (or within certain interior portions of the board) to cooperatively and selectively interconnect to form one or more desired electrical circuits. This communication and interconnection may require the use of shared electrical ground planes, the transmittal of electrical power and/or control type signals between each of the component containing surfaces and/or the component containing board portions, and/or the selective and physical connection of various contained components.
This desired interconnection typically requires one or more vias, apertures and/or holes to be drilled, etched and/or formed through the core of the circuit board substrate, thereby Selectively creating one or more vial, apertures and/or holes which pass through and/or traverse some or all of the component containing surfaces and/or layers of the circuit board. The vias are then typically filled with solder (e.g., a pin or component connector is soldered into the hole). In this manner, electrical connections are made or formed which connect electrical components and/or circuitry to the core of the circuit board substrate, or to other components and/or circuitry located on the opposing side or surface of the board.
It is further desirable to form xe2x80x9cair-bridgesxe2x80x9d or xe2x80x9ccrossoverxe2x80x9d type circuits upon and/or within the various surfaces, layers and/or component containing portions of the formed circuit board in order to allow multiple layers or levels of circuits and/or electrical interconnections to be formed upon a single board surface and/or within a component containing portion of the circuit board. In this manner, an increased amount or quantity of the electrical circuits may be created or formed upon and/or within the circuit board, thereby desirably increasing the density of the contained circuitry.
Prior methods for physically and electrically interconnecting layers or portions of multi-layered circuit boards are often relatively complicated, costly and time consuming. These prior methods have also resulted in relatively unreliable or defective connections to be formed, thereby causing certain portions of the formed circuit boards to be unusable or to malfunction.
There is therefore a need for a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior circuit boards and which utilizes xe2x80x9cviasxe2x80x9d and/or xe2x80x9cair bridgesxe2x80x9d in a relatively uncomplicated and cost effective manner to form highly reliable physical and electrical interconnections between one or more layers of electrical circuitry.
It is a first object of the present invention to provide a method for producing a multi-layer electrical circuit board that overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques.
It in a second object of the invention to provide a method for producing a multi-layer electrical circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electrical circuit board forming methodologies and techniques and which allows for the selective, efficient, and reliable interconnection between some or all of the various component containing surfaces and portions of the formed multi-layer electrical circuit board.
According to a first aspect of the present invention, a method for forming a connection within a multi-layer circuit board is provided. The multi-layer circuit board includes a core member having a top surface and a bottom surface, and first and second conductive members, which are respectively attached to the top and the bottom surface of the core member. The method includes the steps of: selectively removing a portion of the core member, effective to cause a portion of the first conductive member to form an air bridge over the second conductive member; providing a bonding tool; imparting a force upon the air bridge by use of the bonding tool, the force being effective to collapse a portion of the air bridge; and bonding the collapsed portion of the air bridge to the second conductive member, thereby connecting the first conductive member to the second conductive member.
According to a second aspect of the present invention, a multi-layer circuit board assembly is provided. The circuit board assembly includes a first circuit portion having a top surface and a bottom surface; a first pre-circuit assembly which is attached to the top surface of the first circuit portion and which includes a top conductive layer; a second pre-circuit assembly which is attached to the bottom surface of the first circuit portion and which includes a bottom conductive layer; an aperture which is formed through the first circuit portion, the first pre-circuit assembly and the second pre-circuit assembly; and a plurality of tab portions which are integrally formed from the top conductive layer, which extend through the aperture and which are coupled to the bottom conductive layer, thereby connecting the top conductive layer to the bottom conductive layer.
These and other objects, aspects, and advantages of the present invention will become apparent upon reading the following detailed description in combination with the accompanying drawings.